The authorities in Long Island (NY) are using drones, helicopters and boats to patrol their beaches after four cases of non-fatal shark bites were confirmed this week and 50 sand sharks were locatedwhich are commonly found in warm or temperate waters and so named because of their tendency to migrate to coastal habitats.

The group of sand sharks was located by a drone on Tuesday the same day two 15-year-old teens and two adults were bitten while swimming at different Long Island beaches, the media reported.

A fifth case was also reported on Tuesday and authorities said the cuts to the knees were caused by “a large marine animal”, believed to be a shark. One of the towns on alert for the presence of sharks is Hempstead, that reported that they plan to use more drones, jet skis and boats to patrol the waters to track the sharks.

Lifeguards will be trained to identify shark dorsal fins, shark presence and swimming pattern. Police urged the public to continue to enjoy the beach, but asked swimmers to watch out for sharks and groups of fish that might attract them. Several non-fatal bite cases were also reported last year, forcing the closure of several beaches on Long Island.